I think this is a weird case of almost Schrodinger style duality. On the one hand, yes, we are talking about a fictional character in a fictional world and that language has probably, as far as we can extrapolate, expanded to include new definitions. Likely, a new term or cannibalism has expanded to include such acts.Except that we're talking about an event that occurred in the fictional world, so those are the rules that apply. It isn't treason in our world to act as a traitor against the fictional United Federation of Planets - but it certainly would be for characters in the show.
On the other side is the fact that we are an audience in the 21st century who do not current inhabit that world. We see the world through that lens, those definitions of our world, and those definitions encompass 21st understanding.
Ultimately, individuals will regard Georgiou in both ways and try to sort it out. From Georgiou's point of view she not a cannibal, as that was not part of her morality to regard Kelpians as on the same level as her own kind. Even if we, the audience, regard it as evil, that is based upon our own morality. And, now that she is in the Prime Universe we can absolutely judge her by that standard with her behaviors in the Prime Universe. But, from her point of view, this standard of morality is completely new.